Two cycle internal combustion engines are commonly fueled with variable boiling point liquid fuel: Starting of these engines when cold or at temperatures other than the normal operating temperatures requires the addition of extra liquid fuel into the combustible fuel-air mixture. The additional fuel is required to provide a sufficient quantity of vaporized fuel in the combustion air being conveyed to the combustion chamber. The conventional choke for controlling mixture enrichment is sometimes supplemented by a primer in order to inject the liquid fuel directly into the intake passage or transfer passage on the engine. It is difficult to determine when the correct amount of liquid fuel has been conveyed to the engine and frequently results in starting difficulty especially for those unskilled in determining whether the failure to start results from an inadequate or overabundant amount of liquid fuel. Since starting cannot occur if the air-fuel mixture reaching the sparkplug is leaner than the lean flammability limit, it is standard practice to instruct the operator to use sufficient choke and/or priming to provide a mixture sufficiently rich to be richer than the lean flammability limit. Since only the vaporized fuel contributes richness to the mixture, and the amount of fuel which vaporizes is dependent on temperature as well as the volatility of the fuel, it is difficult to provide choking and/or priming instructions which assure starting over the range of temperatures and fuel volatility normally encountered in starting engines. As a result, excessive choking or priming frequently occurs which results in a puddle of liquid fuel accumulating at the low point of the crankcase commonly known as flooding. This condition is corrected by continued rotation of the engine with the choke open and no additional fuel added until sufficient air has passed through the engine to lean-out the mixture within the limits of flammability. This frequently requires additional manual engine rotation beyond the patience and endurance of the operator.